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Given a binary search tree, write a function kthSmallest
to find the kth smallest element in it.
Example 1:
Input: root = [3,1,4,null,2], k = 1
3
/ \
1 4
\
2
Output: 1
Example 2:
Input: root = [5,3,6,2,4,null,null,1], k = 3
5
/ \
3 6
/ \
2 4
/
1
Output: 3
Follow up:
What if the BST is modified (insert/delete operations) often and you need to find the kth smallest frequently? How would you optimize the kthSmallest routine?
Constraints:
- The number of elements of the BST is between
1
to 10^4
.
- You may assume
k
is always valid, 1 ≤ k ≤ BST's total elements
.
[Tree]
[Binary Search]
Similar Questions
- Binary Tree Inorder Traversal (Medium)
- Second Minimum Node In a Binary Tree (Easy)
Hints
Hint 1
Try to utilize the property of a BST.
Hint 2
Try in-order traversal. (Credits to @chan13)
Hint 3
What if you could modify the BST node's structure?
Hint 4
The optimal runtime complexity is O(height of BST).